Output Duplicate Row Occurrences In A Table

I want to retrieve staff who attend less than 80% for a meeting type assuming we have 10 meetings per list.

Meeting Table:

staffID list date
------------------------
1 A 2013-01-15
2 B 2013-01-17
1 B 2013-01-17
1 A 2013-01-18
2 B 2013-01-19
1 A 2013-01-20
2 C 2013-01-21

* 1 - Dan
* 2 - Jane

When the staffID occur 3 times (70%), query will Output:

staffName list Participation%
------------------------
Dan A 70

SELECT a.staffName, b.list,
(100 - ((COUNT(c.staffID) * 100) / 10)) AS 'Participation%'
from Staff AS a, listType AS b, Meeting AS c
where a.staffID = c.staffID AND
b.list = c.list
GROUP BY a.staffName, b.list
HAVING COUNT(c.staffID) > 2